Re: [PATCH] target/avr: Ignore unimplemented WDR opcode

[Philippe Mathieu-Daudé]

Cc'ing qemu-trivial@

On 5/5/21 3:35 PM, Fred Konrad wrote:
> Le 5/2/21 à 9:09 PM, Philippe Mathieu-Daudé a écrit :
>> Running the WDR opcode triggers a segfault:
>>
>>    $ cat > foo.S << EOF
>>    > __start:
>>    >     wdr
>>    > EOF
>>    $ avr-gcc -nostdlib -nostartfiles -mmcu=avr6 foo.S -o foo.elf
>>    $ qemu-system-avr -serial mon:stdio -nographic -no-reboot \
>>      -M mega -bios foo.elf -d in_asm --singlestep
>>    IN:
>>    0x00000000:  WDR
>>    Segmentation fault (core dumped)
>>
>>    (gdb) bt
>>       #0  0x00005555add0b23a in gdb_get_cpu_pid (cpu=0x5555af5a4af0)
>> at ../gdbstub.c:718
>>       #1  0x00005555add0b2dd in gdb_get_cpu_process
>> (cpu=0x5555af5a4af0) at ../gdbstub.c:743
>>       #2  0x00005555add0e477 in gdb_set_stop_cpu (cpu=0x5555af5a4af0)
>> at ../gdbstub.c:2742
>>       #3  0x00005555adc99b96 in cpu_handle_guest_debug
>> (cpu=0x5555af5a4af0) at ../softmmu/cpus.c:306
>>       #4  0x00005555adcc66ab in rr_cpu_thread_fn (arg=0x5555af5a4af0)
>> at ../accel/tcg/tcg-accel-ops-rr.c:224
>>       #5  0x00005555adefaf12 in qemu_thread_start
>> (args=0x5555af5d9870) at ../util/qemu-thread-posix.c:521
>>       #6  0x00007f692d940ea5 in start_thread () from
>> /lib64/libpthread.so.0
>>       #7  0x00007f692d6699fd in clone () from /lib64/libc.so.6
>>
>> Since the watchdog peripheral is not implemented, simply
>> log the opcode as unimplemented and keep going.
>>
>> Reported-by: Fred Konrad <konrad@adacore.com>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>   target/avr/helper.c | 6 +-----
>>   1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/target/avr/helper.c b/target/avr/helper.c
>> index 35e10195940..981c29da453 100644
>> --- a/target/avr/helper.c
>> +++ b/target/avr/helper.c
>> @@ -188,11 +188,7 @@ void helper_break(CPUAVRState *env)
>>     void helper_wdr(CPUAVRState *env)
>>   {
>> -    CPUState *cs = env_cpu(env);
>> -
>> -    /* WD is not implemented yet, placeholder */
>> -    cs->exception_index = EXCP_DEBUG;
>> -    cpu_loop_exit(cs);
>> +    qemu_log_mask(LOG_UNIMP, "WDG reset (not implemented)\n");
>>   }
> 
> Seems ok to me, at least better than having a segfault.
> 
> Reviewed-by: KONRAD Frederic <frederic.konrad@adacore.com>
> 
>>     /*
>>
>